Furnace clean and tune. Cycled system. Checked heat exchanger, found some rusting and damage. Checked and cleaned burners and flame sensor. Burners are worn. Flame sensor is ok. Found igniter worn. Ventor motor is very worn and has major noise and vibration issues due to worn and damaged bearings. Checked levels of CO and XS air in exhaust. CO and XS air are elevated possibly due to blockage in secondary heat exchanger. No CO found in airstream. Average life of this unit is 14 years. This system is 26+ years old and worn. Even tho this unit is operating normal at this time, failure is expected. Job complete.